Power operated fastener driving devices are in widespread use in the construction and building trades and typically include a power operated driving mechanism mounted within a housing that powers the driving movement of a drive element slidably mounted within a drive track that extends through a nose piece mounted to the housing. Typically when the driving mechanism is actuated, the drive element moves in a fastener driving direction through a drive stroke and then moves in the opposite direction through a return stroke during one cycle of operation. A trigger mechanism that is movable through an actuation stroke is commonly provided on the exterior of the housing to initiate an operating cycle.
A magazine assembly mounted to the housing supplies a series of fasteners to the drive track through a lateral opening in the same and the leading fastener in the drive track is driven outwardly of the drive track into a workpiece by the driving movement of the drive element when the driving mechanism is actuated. Typically a spring biased fastener feeding device advances the fasteners through the magazine toward and into the drive track.
It is not desirable to actuate the driving mechanism when there is no fastener in the drive track or when the drive track is not in contact with a workpiece that will receive the fastener, because it is preferable that the energy transferred to the driving element and related structures during the drive cycle be absorbed by the movement of the fastener into the workpiece. When no fastener is present in the drive track when the driving mechanism is actuated, for example, the driving device must absorb all of the energy generated during the drive stroke and this subjects the device to an undesirable level of stress. It is also undesirable to actuate the driving mechanism when no fastener is in the drive track and the nosepiece is against the workpiece because the driving element typically extends out of the nosepiece when the driver is at the lowermost point of its power stroke so that the fastener can be driven flush or countersunk in the workpiece. Thus, if no fastener is present in the drive track, the driving element will mar the surface of the workpiece.
Power operated fastener driving devices typically include a trip assembly mounted on the nosepiece and operatively associated with the trigger mechanism to prevent the driving mechanism from being actuated when the nosepiece is not in contact with a workpiece. Typically, when the nosepiece is placed in contact with the workpiece, the trip assembly moves with respect to the workpiece and places the trigger mechanism in an active condition so that the driving mechanism can be actuated by movement of the trigger mechanism through its actuation stroke. Conventionally constructed trip assemblies do not prevent the driving mechanism from being actuated when the magazine is removed from the housing and/or the magazine is empty or nearly empty to prevent actuation of the driving mechanism when there is not fastener in the drive track, however, and this is a significant shortcoming of prior trip assembly design because it can result in damage to or marring of the surface of the workpiece. A need exists, therefore, for a power operated fastener driving device that cannot be actuated when the magazine is removed from the housing or when the magazine is empty or nearly empty.
Often the trip assemblies of fastener driving devices include adjustable mechanisms that can be adjusted to control the depth to which a fastener is driven into the workpiece. Typically these adjustments to a trip assembly require the use of hand tools and are time consuming to effect. A need exists for a trip assembly that can be easily adjusted manually without the use of hand tools to change the depth to which the fasteners are driven.